Indonesian divers in the Java Sea have recovered the second black box flight recorder of AirAsia flight QZ8501 that crashed more than two weeks ago.

The cockpit voice recorder has been found at around 30m away from where the flight-data recorder was recovered earlier this week.

The air crash investigation team in Jakarta have downloaded data from the flight data recorder and are working to analyse up to 25 hours of data from indicators that focus on the speed, altitude and engine temperature of the aircraft before it crashed.

"In one week, I think we will be getting a reading."

National Transportation Safety Committee lead investigator Mardjono Siswosuwarno was quoted by Reuters as saying: "In one week, I think we will be getting a reading."

The team is preparing to download data from the cockpit voice recorder, which stores two hours of conversations on the flight deck.

The black box recorders will help investigators identify the cause of the crash.

Halfway on its two-hour flight to Singapore from Surabaya, the A320-200 ran into trouble and lost contact with the air traffic control. The aircraft was carrying 155 passengers and seven crew members on-board.

So far, 48 bodies of passengers and crew have been recovered and those missing could be trapped inside the aircraft.